Electronic fuel injection systems can be divided into two basic types. One type is a multi-point fuel injection system where each engine cylinder has associated with it an individual fuel injector that controls the injection timing and fuel metering for that cylinder. The other basic type is a single-point injection system where the fuel supplied to a plurality of engine cylinders is controlled by one or two injectors that are shared by the cylinders.
In a typical single-point fuel injection system the one or two fuel injectors are located upstream of the intake manifold. The actuation of each fuel injector is controlled by an electrical single from an engine control unit. The engine control unit is an electronic logic device, either programmable or hard wired, that controls fuel injection on the basis of several operating variables, including engine RPM, temperature, speed command, manifold air pressure and the like. The fuel injector is conventionally an electromagnetic valve this is open through the time duration of the signel from the engine control unit. The opening and closing of the fuel injector causes it to output a pressurized fuel pulse or charge of discrete time duration. This discrete fuel charge is provided to an atomizer where it is mixed with air. The air/fuel (A/F) mixture from the atomizer flows to the intake manifold, where it is drawn into the cylinders by the effect of passing through a decreasing pressure gradient.
There are at least two important reasons why single-point fuel injection is preferable over multi-point fuel injection. First, and of major importance, is the reduction in cost that is achieved when a separate fuel injector no longer needs to be provided for each individual engine cylinder. Instead, one fuel injector may service a plurality of engine cylinders and a considerable cost savings can be realized. Secondly, the single point fuel injection system facilitates more complete atomization of the fuel with air. More specifically, in a multi-point fuel injection system, each fuel injector is in close physical proximity to its respective engine cylinder and the injected fuel has less time to atomize before reaching the cylinder. However, in a single-point fuel injection system the fuel injector is positioned upstream of the intake manifold and the injected fuel has a relatively longer opportunity to atomize and become uniformly mixed before being drawn into the engine cylinders.
A special case of a single-point fuel injection system is a single-injector, single-point system. This is defined as a single-point fuel injection system where a single fuel injector services all of the cylinders in the engine. This type of system has the added advantage of requiring only a single fuel injector, and approaches an optimal cost reduction in electronic fuel injection design.
It is desirable in a single-point fuel injection system to provide some means intermediate the fuel injector and intake manifold to effectively stretch the time duration of the discrete, pressurized fuel charge output by the injector. By stretching the discrete fuel charge towards a more continuous flow, there will be less variation in the ratio of the A/F mixture passing through the intake manifold through each injection cycle. A uniform A/F ratio tends to improve engine performance and provides better emission control.
The present invention addresses the matter of uniform A/F ratio in a single-point electronic fuel injection system by making as its objective the design of a fuel injection flow regulating device that functions to moderate the discrete, pressurized fuel pulse from the injector into a more continuous fuel flow.